Recently, transparent colored glass, produced by imparting color to glass, has been widely used for interior and exterior building materials. For example, colored glass coated with paint, laminated glass comprised of two sheets of glass with a resin or film interposed therebetween, colored glass manufactured by adding metal additives to glass, or the like are used. However, the colored glass coated with the paint has a blocking property by which light does not entirely pass through the glass due to the size of pigments attached to the glass. The laminated glass not only exhibits color but also maintains transparency since a transparent color resin or film is disposed between two sheets of glass. However, due to use of a dye vulnerable to ultraviolet light in order to exhibit color, the laminated glass rapidly fades over time as compared with glass using a pigment. Thus, a metal additive-based colored glass is widely used for interior and exterior building materials since it can exhibit any color while having transparency, and is resistant to ultraviolet rays.
However, since the metal additive-based colored glass currently used for interior and exterior building materials contains heavy metals, it causes environmental contamination. Further, due to restricted production in view of economic feasibility, the metal additive-based colored glass is produced/sold with limited colors such as green, blue and bronze, and thus does not properly meet consumer demand for color variety.
To solve such problems, studies have been conducted to develop coating compositions that exhibit a variety of colors and maintain transparency in coating glass.
Korean Patent Publication No. 10-2004-0072338 discloses an organic-inorganic composite resin used as a binder to have excellent adhesion, heat resistance and solvent resistance and a proper transparent pigment used to impart various colors.
In coating glass, when the organic-inorganic composite resin is used to have excellent adhesion, heat resistance and solvent resistance and the pigment for impart color to the resin is properly dispersed, the glass exhibits the color while maintaining transparency. However, since most pigments have a considerably small particle size, e.g., 0.01 μm or less, the pigments are likely to be agglomerated and have reduced dispersion stability due to decrease in compatibility with the organic-inorganic composite resin, causing an increase in the size of pigment particles and deteriorating transparency.